Multi-opening optical devices, comprising a plurality of optical systems such as lenses forming an array, are used in many fields of optics and photonics. Examples of applications are artificial eyes, cameras (for example Lytro or Pelican Imaging plenoptical optics), 3D optical imaging systems (capture or projection of images), or even telecommunications.
There are different technical solutions for varying the focal length of an optical device comprising a plurality of lenses.
A first technique consists of forming a plurality of lenses by electrowetting. The optical device can be activated by applying a difference in potential between several electrodes (traditional case of electrowetting). Another solution (without electrode) consists of using a Lithium Niobate substrate comprising reversed polarization regions distributed according to a determined pattern and a layer of optical oil spread over the surface of said substrate. A variation in temperature of the substrate modifies its polarization and results in modifying the thickness of oil according to the polarization of the corresponding region of the substrate [1].
Another technique is based on deformation of a deformable membrane in contact with a constant volume of fluid. The optical device comprises a fluid circuit formed by a plurality of chambers intercommunicating via channels, said chambers being delimited between a substrate and a deformable membrane. Each chamber constitutes a lens. The fluid circuit is filled with substantially uncompressible fluid and is connected to a pump which varies the fluid pressure in all the chambers and deforms the membrane to adjust the focal length of the lenses [2].
However, such a device is bulky, especially due to the presence of the pump which is arranged offset relative to the array of lenses.
Also, the fluid circuit, which is complex and costly to make, compromises the response time of the device.